In the case of diesel internal combustion engines of today's motor vehicles, the course of the combustion (combustion process) in the cylinders of the internal combustion engine is adapted by a corresponding presetting of certain parameters that determine the combustion, such as, for example, time of one or more pre-injections, time of the main injection, amount of diesel fuel injected in the pre-injections or in the main injection, injection pressure, or rail pressure of a common rail fuel injection system, in such a way that the cetane number of the fuel that is used can be, for example, in a range of between 51 and 54 without the emissions of the internal combustion engine or the performance of the motor vehicle being adversely affected in any way in the case of a change in the cetane number within this range.
Based on more recent emission requirements, e.g., BIN 5, diesel fuels are increasingly being used, however, in which the cetane number is less than 50, with primarily in the U.S.A., diesel fuels with cetane numbers of below 40, up to 38, being used. For such a large fuel range comprising fuels with cetane numbers of between 54 and 38, however, none of the parameters determining the combustion, which allow for all of these fuels to achieve satisfactory results with respect to the emissions and the performance, can be found any longer.
Based on this, the object of the invention is to provide a method and a device of the above-mentioned type with which, in the event of a change in the cetane number of the fuel that is used, an adaptation that takes this change into account can be made to the combustion process in the cylinders of the internal combustion engine to avoid a deterioration of emissions or an impairment of the performance.